Test sender connect and recv errors. Remove file on 400 respose. Stop sending on 500 response. Limit number of errors.
Test 500 errors and bad files.
Switch back to github.com/go-sql-driver/mysql from github.com/arnehormann/mysql.
Merge pull request #90 from percona/pct-764-bad-data-files

PCT-764: Bad data file causes agent to stop sending but keep spooling data